585
FXUS65 KBYZ 111831
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
1231 PM MDT FRI SEP 11 2026
KEY MESSAGES
- COOLER WEATHER THROUGH THE MIDDLE OF NEXT WEEK, WITH THE
EXCEPTION OF A WARMER DAY SUNDAY.
- OCCASIONAL CHANCES OF SHOWERS (MAINLY LIGHT) THROUGH SUNDAY
NIGHT. SCATTERED THUNDERSTORMS POSSIBLE IN SOUTHEAST MONTANA
SUNDAY NIGHT, SOME POSSIBLY STRONG.
- PERIODIC LOW CLOUDS AND POSSIBLE FOG ALONG THE WESTERN FOOTHILLS
TONIGHT THROUGH EARLY SUNDAY.
- BREEZY WEST WINDS MONDAY; GUSTS NEAR 50 MPH ALONG THE WESTERN
FOOTHILLS.
DISCUSSION
THROUGH NEXT FRIDAY...
SATELLITE IMAGERY SHOWS A WEAK SHORTWAVE PUSHING WEST-TO-EAST THRU
CENTRAL MT, AND IN FACT POST-FRONTAL SHOWERS HAVE SOMEWHAT
OVERACHIEVED IN NW PORTIONS OF THE FORECAST AREA THIS MORNING.
RAINFALL AMOUNTS OF 0.02-0.08" HAVE BEEN MEASURED IN NORTHERN
SWEET GRASS, WHEATLAND AND GOLDEN VALLEY COUNTIES AS OF 1630Z.
ISOLATED TO SCATTERED MAINLY LIGHT SHOWERS WILL CONTINUE TO SPREAD
EASTWARD THIS AFTERNOON AND EVENING. TONIGHT INTO EARLY SATURDAY,
THIS WILL EVOLVE INTO SOME SHOWERS ALONG A MID LEVEL WARM FRONT
OVER SOUTHEAST MT, AS WE START TO BUILD HEIGHTS BEHIND THIS
INITIAL WAVE. THE PRECIPITATION WILL BE WELCOMED BUT NOT
SIGNIFICANT.
THE OTHER ITEM TO NOTE ON SATELLITE IMAGERY IS UPSLOPE LOW CLOUDS
FORMING ALONG N-NE ASPECTS OF THE BEARTOOTH AND PRYOR MOUNTAINS,
WITH CEILINGS OF 3000-4000 FT AGL. AS UPSLOPE FLOW DEEPENS THIS
STRATUS SHOULD CONTINUE TO EXPAND, AND WILL BE A MODEST ISSUE WITH
REGARD TO AVIATION IN THE SHORT TERM PERIOD. THE PERSISTENT
EASTERLY WINDS SHOULD KEEP SOME COMPONENT OF LOW STRATUS INTO
SUNDAY MORNING, WITH PERHAPS FOG ALONG THE IMMEDIATE EASTERN
SLOPES TONIGHT AND AGAIN SATURDAY NIGHT. WILL BE SOMETHING TO
MONITOR. ALSO, AS A RESULT OF THE UPSLOPE WINDS, CLOUD COVER AND
POOR MIXING, HAVE CONFIDENTLY DROPPED FORECAST HIGH TEMPS A FEW
DEGREES BELOW THE TYPICAL GUIDANCE.
AS HAS BEEN THE TREND THE PAST FEW DAYS, THE DEVELOPING LOW OVER
THE PACNW IS EXPECTED TO TRACK WELL TO OUR W/NW THIS WEEKEND, JUST
CLIPPING FAR NORTHWEST MT BEFORE ENTERING SOUTHERN AB LATE SUNDAY.
THIS IS A DRY TRACK FOR OUR FORECAST AREA AND POP/QPF FORECASTS
REFLECT A CONTINUED DOWNWARD TREND. TEMPS WILL BE COLD ENOUGH FOR
HIGH ELEVATION SNOW SHOWERS OVER THE WESTERN MOUNTAINS SUNDAY
NIGHT INTO MONDAY, BUT THE AIR MASS IS LOOKING DRY DURING THIS
TIME PERIOD SO SNOW IS LOOKING LIKE A NON-ISSUE.
ALL OF THAT SAID, THERE MAY BE A RISK OF STRONG T-STORMS OVER
SOUTHEAST MT SUNDAY NIGHT WE SEE THETA-E RETURN IN A PRE-FRONTAL
ENVIRONMENT. THERE REMAINS UNCERTAINTY WITH REGARD TO WHERE A
SURFACE LOW DEVELOPS (CONSENSUS IS FOR NORTH CENTRAL WY) AND HOW
MUCH SURFACE HEATING WE SEE ON SUNDAY, BUT THE OVERALL CONVECTIVE
SIGNALS SUGGEST THIS IS SOMETHING TO WATCH. WITH OR WITHOUT
T-STORMS, SCATTERED POPS SHOULD SUFFICE IN THE EAST SUNDAY NIGHT
WITH PWATS RISING TO 1+" GIVING SUPPORT FOR LOCALIZED MODERATE TO
HEAVY RAINFALL, ALBEIT BRIEFLY. AS A SIDE NOTE, 700MB PLUME TO
+12C WOULD SUPPORT SURFACE TEMPS INTO THE 80S IN OUR SOUTH IF SW
WINDS ARE MIXED INTO (DO NOT THINK THIS WILL HAPPEN). REGARDING
FIRE WX, THE INCREASING PRE-FRONTAL MID LEVEL SW WINDS WILL LIKELY
RESULT IN ELEVATED FIRE CONCERNS OVER THE HIGH ELEVATIONS OF THE
GALLATIN NF.
MONDAY WILL BE DRY, COOLER & BREEZY BEHIND A PACIFIC COLD FRONTAL
PASSAGE SUNDAY NIGHT. GIVEN THE TRACK OF THE CLOSED LOW TO OUR
NORTH THE WIND SIGNAL FOR MONDAY HAS STRENGTHENED, WITH ENSEMBLES
SHOWING GUSTS ~50 MPH ALONG THE WESTERN FOOTHILLS, AND 30-40 MPH
FURTHER EAST. DO NOT SEE ENOUGH MID LEVEL FLOW FOR WIND HIGHLIGHTS
AT THIS TIME, BUT GUSTY CROSSWINDS MAY IMPACT TRAVEL ALONG I-90
AND US-191. LOOK FOR TEMPS IN THE 60S TO LOWER 70S MONDAY. LIGHTER
WINDS AND CLEAR SKIES MAY YIELD FROST IN NOTORIOUSLY COLDER SPOTS
MONDAY NIGHT. PROBABILITIES FOR A LOW TEMP OF 36F OR COLDER IS
20-40% AT THESE LOCATIONS.
NW FLOW BEHIND THE DEPARTING LOW WILL KEEP TEMPS A LITTLE COOLER
THAN NORMAL THROUGH MIDWEEK. ANOTHER SHORTWAVE DROPPING OUT OF
WESTERN CANADA BRINGS A CHANCE (15-25%) OF LIGHT PRECIP TUESDAY
NIGHT AND WEDNESDAY, BUT MODELS ARE IN STRONG DISAGREEMENT IN
TIMING AND STRENGTH OF A MIDWEEK SHORTWAVE. HIGHER HEIGHTS SHOULD
PUSH TEMPS BACK TO THE 70S OR NEAR 80F LATE WEEK, BUT ANOTHER WEAK
TROF FROM THE WEST MAY BRING MORE SHOWER POTENTIAL BY FRIDAY.
JKL
AVIATION
BREEZY NORTH TO EAST WINDS WILL GRADUALLY DECREASE THIS EVENING.
SHOWERS AND ISOLATED THUNDERSTORMS WILL WORK THROUGH THE AREA FROM
WEST TO EAST INTO THIS EVENING, GRADUALLY LIFTING TO THE NORTHEAST
OVERNIGHT. LOCAL MVFR CONDITIONS ARE POSSIBLE WITH THE
SHOWER/THUNDERSTORM ACTIVITY. CEILINGS OVER WESTERN AND CENTRAL
AREAS WILL GRADUALLY LOWER INTO THIS EVENING AND OVERNIGHT TO
MVFR AND POTENTIALLY IFR. CONFIDENCE IN LOW CLOUDS CAUSING
REDUCTIONS IS GREATEST FOR KLVM TO K6S0 AND KHWQ. PATCHY FOG IS
POSSIBLE IN UPSLOPE AREAS ACROSS THE WEST OVERNIGHT AS WELL,
PRODUCING LOCAL IFR CONDITIONS. STP
PRELIMINARY POINT TEMP/POPS
SAT SUN MON TUE WED THU FRI
-----------------------------------------------------------
BIL 048/066 046/071 048/068 043/068 043/067 044/076 049/076
31/E 00/B 20/N 00/U 01/B 00/U 22/W
LVM 044/065 044/073 041/065 036/067 039/068 040/076 045/076
41/E 01/N 20/N 00/U 01/B 11/U 22/T
HDN 045/070 043/076 043/071 037/071 040/069 040/078 041/078
41/B 00/B 20/N 00/U 00/B 00/U 22/W
MLS 047/064 047/072 050/070 041/068 046/070 044/076 048/076
02/W 10/N 61/N 00/U 11/B 00/U 12/W
4BQ 048/067 048/075 051/072 041/070 047/072 044/077 048/077
31/E 11/B 40/N 00/U 10/B 11/U 22/W
BHK 042/064 041/070 047/071 038/069 041/071 040/077 045/078
02/W 21/N 71/N 00/U 22/W 10/U 12/W
SHR 043/071 042/079 046/070 036/071 039/069 038/077 043/076
20/B 00/B 30/U 00/U 01/U 11/U 22/W
BYZ WATCHES/WARNINGS/ADVISORIES
MT...NONE.
WY...NONE.
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